Organic phosphorus compounds for increasing the flame resistance of textiles and method of applying the same



Patented Oct. 12, 1954 ORGANIC PHOSPHORUS COMPOUNDS FOR INCREASING THEFLAME RESISTANCE OF TEXTILES AND METHOD OF APPLYING THE SAME Donovan E.Kvalnes, Penns Grove, and Neal 0. Brace, Woodstown, N. .I., assignors toE. I. du Pont de Nemours & Company, Wilmington, DeL, a corporation ofDelaware No Drawing. Application October 23, 1951, Serial No. 252,811

6 Claims. 1

This invention relates to organic compounds containing phosphorus andparticularly to such compounds which also contain a grouping which is anaddition product of two isocyanate radicals. It further relates to neworganic compounds which are useful in increasing the flame resistance oftextiles.

Phosphorus compounds, and particularly organic phosphorus compounds,have been applied to fabrics and films to obtain a variety of usefuleffects such as flame resistance, anti-static prop erties andinsect-proofing. These effects however have not been permanent, as thetreating agents are ordinarily removed by laundering or by dry-cleaning.

Efforts have been made to overcome this fault by applying the phosphoruscompounds in company with resins to fasten the compounds to the surface.While this has resulted in some improvement, the durability of thefabric so treated is not great and repeated laundering or drycleaningremoves the surface treatment. It has been recognized that if thephosphorus compounds could be attached to the surface of the fabric orfilm by a true chemical union, a permanent effect could be obtained.Heretofore all such attempts have resulted in the severe tendering ofthe fabric due to the strenuous conditions needed to bring aboutchemical reaction. Such treatments are obviously not practical.

It is an object of this invention to provide a new series of organicphosphorus compounds which may be applied to textiles and which may bechemically bonded thereto without injury to the textile. A furtherobject is to provide organic phosphorus compounds which are not removedby repeated launderings after bonding to the fabric. A further object isto provide a process of bonding the new phosphorus com; pounds of thisinvention to textile material's. Further objects will appear from thedetailed description of this invention which follows.

The new compounds of this invention are those in which phosphorus ispresent in the form of a phosphate, p-hosphonate, phosphinate orphosphin oxide radical and in which there also occurs the bivalentgrouping --RDR', R. and R. representing aryl radicals and D representingan addition product of two isocyanate radicals.

The radical containing phosphorus may be represented gene-rally by theexpression:

in which A contains from 1 tol2 carbon atoms and is a member of thegroup consisting of alkyl and alkoxy radicals, B contains from 1 to 12carbon atoms and is a member of the group consisting of alkyl, aryl,alkoxy and aryloxy radicals, and m is an integer from 0 to l. Theradical may be a phosphate group, for example, using methyl as thehydrocarbon part of the substituents:

such as methyl ethyl, .propyl, isopropyl, n-butyl, hexyl, octyl, ordodecyl, or the corresponding alkoxy radicals. They may be the same ordifferent. Alternatively, B may be an aryl radical such as phenyl,tolyl, xylyl, naphthyl, biphenyl and the like or the correspondingaryloxy radical.

The group -D-, representing an addition product of two isocyanateradicals, probably has one of the following structures:

p The addition product maybe formed by the catalytic dimerization ofaromatic isocyanates, preferably in the presence of a catalyst such asphenyldimethylphosphine, as disclosed in copending application SerialNo. 248,270 of Otto .Stallmann, filed Sept. 25, 1951. Whatever theirstructure, these dimeric addition products do not share the well-knowninstability of monomeric isocyanates with respect to water and '3 othermaterials containing active hydrogen and they may be stored withoutspecial precautions and without deterioration. They may however beruptured by heating them to a temperature of 125 to C. By thistreatment, reactive groups are formed which react readily with compoundscontaining active hydrogen atoms such as are present in amine, amide,hydroxyl and carboxyl radicals. Phosphorus compounds containing suchdimeric isocyanate addition products may therefore be applied to fabricsor films composed of such materials as cotton, wool or where D is againused to indicate an addition product of two isocyanate radicals. Thephosphorus compounds which are useful in this reaction may berepresented by the formula in which A, B and m have the significancedescribed above, X is a bivalent organic radical containing from 1 to 12carbon atoms, Y is the residue obtained by removing a single hydrogenfrom a member of the class of functional groups containing activehydrogen consisting of primary amino, secondary amino, primary amido,secondary amido, hydroxyl and carboxyl groups, and n is an integer fromto 1, the value of n being at least as great as that of m. Compounds ofthis sort may be obtained by the action of a substituted phosphorylchloride on a polymethylene glycol or other compound containing ahydroxyl group and a carboxyl, amino or amido radical. In compoundsprepared in this manner, the phosphorus atom will be linked to theradical X through an oxygen atom, i. e., m will be 1. Compounds in whichthe phosphorus is linked directly to the radical X, i. e., where m is 0,may be ob tained through a Grignard reaction between a phosphorylchloride and the Grignard reagent formed from an alkyl halide which alsocontains a hydroxyl, carboxyl, amino or amido group.

The expression Y includes the following radicals: O-, NH--, -COO, CONH.--NR and CONR, where R is an alkyl. aryl or cycloalkyl radicalpreferably containing no more than 12 carbon atoms. The bivalent organicradical X may be aliphatic, cycloaliphatic, aromatic or a combinationthereof. It may contain a carbon chain which is interrupted by heteroatoms or groups such as O, -S--,

CO-, -S0z and the like. The carbon skele ton of this radical may also besubstituted with groups such as ether, ester, halogen or nitro. Theradical X need not be present at all in the phosphorus compound, inwhich case n is zero. In this case m is also zero, since n must be atleast as great as m. Examples of such compounds in which m and n arezero are diethylphosphoric acid and dimethylphosphoryl amide.

The aromatic diisocyanate dimers which may be reacted with thephosphorus compound are prepared by known methods from monomericdiisocyanates or mixtures of diisocyanates. At least one of theisocyanate groups present in the monomeric diisocyanate must be attachedto an aromatic ring. Compounds of this type include 2,4-tolylenediisocyanate, 4-ch1oro-1,3-phenylene diisocyanate,2-cl1loro-1,4-phenylene diisocyanate, Z-methoxy-lA-phenylenediisocyanate and 2-nitro-1,4-phenylene diisocyanate. Other usablediisocyanates include compounds such as oon- NCO on ooNONc-o or NCO INCO in which Y represents an ester group such as -OOCR or COOR and inwhich R represents an alkyl, aryl, aralkyl or cycloalkyl group of from 1to 10 carbon atoms. The aromatic nucleus may also be substituted with atertiary amino group as in the compound IITRrR-a NCO in which R1 and R2represent alkyl, aryl, aralkyl or cycloalkyl groups. the total number ofcarbon atoms in R1 and R2 being from 2 to 12. Other diisocyanatescontaining a single phenyl group which are useful in the process of thisinvention are O O N-cyclohexyl in which X represents 0, S, CO, S02 or(CHZM, and similar compounds in which X represents an alkylene groupwhich is interrupted by a hetero atom such as oxygen, sulfur ornitrogen. In these compounds 12. may be from 1 to 12. The diisocyanatesmay contain naphthyl groups as in (fCHa NCO $0113 NCO NCO NCO ora'plurality of phenyl groups as in NCO where X is O, S, 00, S02, CH=CH,N=N, (CHz)n or an alkylene group which is interrupted by a hetero atomsuch as oxygen, sulfur or nitrogen, where Y is a saturated orunsaturated hydrocarbon group, an ether group, an ester group, atertiary amino group, -NCS, halogen or nitro, .and where n is from 1 to12.

I The new compounds of this invention includes those having the generalformula A preferred compound of this type is that obtained from thereaction of ethylene glycol with diethylchlorophosphate and with thedimer of 2,4-tolylene diisocyanate. This compound has the formula 0o2H5o roozHloooNH 'D When p equals zero, the compounds of this class arederived from mono-isocyanates and have the general formula Examples ofthis type of compound arethe dimer of 4 isocyanatophenyldiethylphosphineoxide, the dimer of4-isocyanatophenyldiisopropyl phosphate, and thedimer of l-isocyanatophenylethylenephenylmethylphosphine oxide.

It is obvious that compounds within the scope .of this invention whichcontain more than two phosphate, phosphonate, phosphinate or phosphineoxide groups or more than one isocyanate addition product per moleculewill have the same general Properties and utility as will compoundshaving precisely these proportions. Such compounds may be formed forexample from the reaction of a trior tetrahydroxy compound with asubstituted phosphoryl halide and a dimeric diisocyanate.

The new compounds of this invention may be prepared by reacting anorganic phosphorus compound containin an amino group attached to anaromatic ring with phosgene to convert it to the correspondingisocyanate, and thereafter dimerizing the isocyanate by known methods.Alternatively, an aromatic diisocyanate may be dimerized and may then bereacted with an organic phosphorus compound containing an activehydrogen group. This reaction is best carried out in a solvent which isfree from active c hydrogen atoms so as to :be non-reactive with theisocyanate group.

The preparation and use of the compounds of this invention areillustrated by the following examples, in which parts are by weight:

Example 1 To 620 parts of ethylene glycol are slowly added 1'73 parts ofdiethylphosphoryl chloride with good agitation. After the evolution ofHCl ceases the excess ethylene glycol is distilled off under vacuum at90-95 C. The syrupy residue is dissolved in 1000 parts of dioxane, 190parts of the dimer of 2,4-anisylene diisocyanate having the formulawhere D is an addition product of two isocyanate radicals, are added,and the mixture is stirred while holding the temperature at 60-65 C. Thecompound of the following structure is formed CHaO- The dioxane isevaporated off on a hot water bath under reduced pressure.

The resulting pasty mass is applied to a fabric by first mixingthoroughly one part with onehalf part of a dispersing agent made bycondensing isooctylphenol with five molecular parts of ethylene oxide,and then dilutin slowly with water with vigorous agitation. The fabricis then padded with this solution, dried and heated to l8.0-190 C. for 3minutes. When cotton cloth is so treated the fabric is flame-retardantand the effect persists after washing. When nylon is .so treated, thecloth is found to possess a very considerable degree of anti-staticproperty which remains after repeated laundering.

Example 2 Eighteen (18) parts of the diethyl ester of methylaminomethylene phosphonic acid,

bath for applying the compound to a cotton fabric. After drying andheating to C. for 2-3 minutes the phosphorus compound has reacted withthe cloth to give a durable flameresistant surface.

Example 3 Twenty (20) parts of 4-hydroxyphenyldimethylphosphine .oxideare dissolved in 200 parts of .d-ioxane and 23.5 parts of the dimer of2,4tolyl- .ene diisocyanate are added and the mixture is The reactionwhere D is an addition product of two isocyanate radicals.

This product is recovered by evaporating off the solvent under reducedpressure.

It may be used to produce anti-static and flame resistant effects onfabric by the procedure illustrated in the previous examples.

The phosphorus compounds containing dimeric isocyanate addition productsmay be applied to fabrics or films from solvents or emulsions, dried andthen heated to about 125 to 200 C. to rupture the isocyanate adducts andthus generate reactive groups, which are presumably nascent NCO groups.These groups will then react with active hydrogens on the surface of thefabric or film to form urethane type linkages, thus chemically bindingthe molecule to the surface. For example, on cotton, viscose rayon andacetate rayon OH groups are available and on nylon :NH groups areavailable and on terephthalic acid polyesters either OH or COOH groupsare available.

The phosphorus compounds thus linked to the surface are not removed byrepeated launderings or dry-cleanings. Ordinary abrasion will not removethem. Removal requires either extreme abrasion or strong hydrolyticconditions, either of which will destroy or practically destroy thesurface as well as the chemical bond between the phosphorus containingmolecule and the surface.

The compounds of this invention may usually be applied to surfaces asemulsions. The emulsion may be made in known ways by use of emulsifyingagents with or without the aid of special machinery. Thus the solid maybe ground finely and dispersed in water with the aid of a 'nonionicemulsifying agent such as the condensation product of oleyl alcohol with1-6-18 moles of ethylene oxide. A colloid mill may be used to aid thedispersion. By a different procedure, an emulsifying agent such asdiethyl cyclohexylamine hexadecyl sulfate may be added to the solventsolution of the compound and then water may be added slowly withvigorous agitation. At first a water-in-solvent emulsion will form whichwill then invert to form a phosphate compound/ solvent-in-wateremulsion. The emulsion may be padded onto the fabric by passing thefabric continuously into the emulsion and then through a nip roll toremove the excess, after which the fabric may be continuously dried at atemperature of not over l105 C. This upper temperature limit isessential so that the diineric compounds are not split prematurely.After drying, the coated fabric is stable under ordinary conditions forat least several days and may be stored and cured when desired. In thecuring or fixation step the fabric may be passed continuously through anoven at 125 to 200-225 C. to cause the dimers to split and allow thereactive groups to combine with the active hydrogen atoms on thesurface.

The impregnation of the fabric may be carried out in various other ways.The emulsion may be sprayed onto the surface or if it is thick it may bespread on with a blade such as a doctor knife.

A solution of the compound in a solvent may be employed but generally anemulsion is preferable since special solvent recovery equipment maythereby be dispensed with.

The extent of the effect which is produced on the fabric by the treatingagents of this invention will be in rough proportion to the amount ofagent applied and to the phosphorus content of the agent. The phosphoruscompounds of this invention ordinarily contain from about 2 to 1.6% byweight phosphorus. Loadings which result in as much as 1.5% phosphorusby weight on the textile usually produce self-extinguishing propertiesin the treated material, while loadings which give from 2.5 to 3%phosphorus on the textile result in excellent flame resistance. Stilllarger amounts may in some cases be applied, up to about 5%. On theother hand, applications of as little as 0.05% by weight of treatingagent produce some anti-static effect and when this is the principalobjective sought, considerably smaller applications of the phosphoruscompounds will be made than when flame resistance is desired.

Polymeric compounds in which both phosphorus-containing radicals anddimeric isocyanate addition products are attached to hydroxylcontainingpolymers such as cellulose, polyvinyl alcohol and the like are disclosedand claimed in our co-pending application Serial No. 252,812, filedOctober 23, 1951.

We claim: I. A compound having the formula 0 A51 0).,.XY0 ONHZ D inwhich A and B contain from 1 to 12 carbon atoms and are members of thegroup consisting of alkyl and alkoxy radicals, m is an integer from G to1, X is a bivalent hydrocarbon radical containing from 1 to 12 carbonatoms, Y is the residue obtained by removing a single hydrogen from amember of the class of functional groups consisting of amino andhydroxyl groups, Z is an aryl radical containing no more than twoaromatic rings and D is an addition product of two isocyanate radicals.

2. The compound having the formula in which D is an addition product oftwo isocyanate radicals.

3. The compound having the formula:

CHsO

in which D is an addition product of two isocyanate radicals.

4. The compound having the formula:

in which D is an addition product of two isocyanate radicals.

5. The compound having the formula:

in which A and B contain from 1 to 12 carbon atoms and are members ofthe group consisting of alkyl and alkoxy radicals, m is an integer from0 to 1, X is a bivalent hydrocarbon radical containing from 1 to 12carbon atoms, Y is the residue obtained by removing a single hydrogenfrom a member of the class of functional groups consisting of amino andhydroxyl groups, Z is an aryl radical containing no more than twoaromatic rings and D is an addition product of two isocyanate radicals,said compound being dispersed in a liquid, and thereafter heating thetreated textile to a temperature from 125 to 225 0.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 2,625,531 Seeger Jan. 13, 1953 2,636,889 Jones et al Apr. 28,1953 OTHER REFERENCES Blair et al., J. Am. Chem. Soc., vol. 56, pp. 907to 910 (1934).

1. A COMPOUND HAVING THE FORMULA
 6. A METHOD OF INCREASING THE FLAMERESISTANCE OF TEXTILE MATERIALS IN WHICH THE FIBER MOLECULES CONTAINSACTIVE HYDROGEN ATOMS WHICH COMPRISES APPLYING TO THE SURFACE OF THESAID TEXTILE A COMPOUND HAVING THE FORMULA